High-frequency coupling condenser



Jan. 7, 1941.

s. I. RAMBO}.

HIGH-FREQUENCY COUPLING CONDENSER Filed Aug. 12, 1938 Fly. 3.

WITNESSES: $2M

I I I INVENTOR 5/76/00/2 l Rambo ATTORN Y Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE 2,228,126 HIGH-FREQUENCY COUPLING CONDENSER Pennsylvania Application August 12, 1938, Serial No. 224,544

4 Claims.

My invention relates to ultra-high-frequency electrical system and, in particular, to structures for circuit elements and supports for electrical discharge tubes in such systems.

One object of my invention is to provide a structure for capacitativelycoupling the output circuit of an electrical discharge tube in an ultrahigh-frequency electrical system with elements of a tuned network to be used in said system.

: Another object of my invention is to form as a compact structure a coupling condenser in the output circuit of an ultra-high-frequency electrical discharge tube.

Still another object of my invention is to pro- 15. vide a compact arrangement which embodies in a single unit a coupling capacitor and a support for an ultra-high-frequency electrical discharge tube.

A further object of my invention is to provide for coupling the output circuit of an ultra-highfrequency electrical discharge tube to a tuned reactor of the transmission line type; that is to say, a tuned element making use of distributed inductance and capacity inherent in a pair of concentric conductors.

Still other objects of my invention will become apparent upon reading the following specification, taken in connection with the drawing in which:

Figure 1 is an elevation, partly in section,

showing an ultra-high-frequency triode supported and coupled to a tuned reactor of the transmission line type in accordance with my invention;

Fig. 2 is a diagram of the pertinent portion of the electrical circuit embodying the elements illustrated in Fig. 1;

Fig. 3 is a side view in detail of the coupling capacitor and anode of the triode; and

Fig. 4 is a top View at right angles to Fig. 3

of the same coupling capacitor and anode.

In ultra-high-frequency electrical circuits, it is necessary to condense into extremely small dimensions the lead-wires interconnecting various impedances and other circuit elements in order that the distributed inductance and capacity of such lead-wires and connections shall be minimized to the greatest possible degree. This is by reason of the fact that even the distributed capacity and inductance of interconnecting leads may form a very large part of the total inductance and capacity of such ultra-high-irequency oscillation circuits, and may even make it impossible to reduce the frequency-determining constants sufiiciently to permit the attainment of the desired frequencies. As a result of the foregoing facts, it becomes necessary to carefully arrange the positions of the various elements traversed by the radio frequency currents of such 5 ultra-high-frequency triodes, and to so design the tube structure, its supports and the structure of the oscillating circuit as to minimize the length of the paths traversed by the high-frequency currents. The foregoing forms a marked 10 contrast to the situation in the case of ordinary radio circuits which employ lumped capacity and inductance as frequency determining elements, and in which the distributed inductance and capacity of the lead-wires may often be ignored. 15

In accordance With my invention, I have devised a tube and circuit structure in Which a coupling capacitor in the output circuit of an ultrahigh-frequency triode, said capacitor constituting a coupling of the triode to a variable re- 20 actance, is compactly formed by employing the sheet of dielectric enclosed between the periphery of a metallic cooling cylinder on the anode of the triode and a ring-shaped clamp directly connected to one element of a reactance of the transmission line type, said clamp also acting as substantially the sole support of the triode.

In this arrangement, the fairly extensive surface Which is inherent in the cooling cylinder forms one plate of the capacitor and the clamp 30 forms the other plate, thus consolidating in a single unit the extended surface necessary for cooling purposes and the extended surface necessary for capacitor purposes and eliminating the use of any lead-wire for connecting the capacitor surface to the anode. The unit similarly makes a double use of the surface area of the clamp so that it performs in addition to its normal function that of providing the cooperating extensive surface required by the capacitor. By thus causing single surfaces to perform a pair of functions which in the prior art have required separate extensive surfaces as Well as interconnecting conductors, the total distributed capacity of 5 the ultra-high-frequency circuit is materially reduced and an arrangement produced which has been found to function most effectively in the ultra-high-frequency field.

With the foregoing principles in mind, Fig. l 50 of the drawing shows a supporting structure I which may be of any suitable material, for example, wood, having shelves 2, '3 for supporting elementsof an ultra-high-frequency electrical circuit. The latter comprises a variable reactor 4 consisting of an outer cylinder 5 of metal and an inner concentric cylinder 6 which may be of the same metal and which is supported from the closed end I of the cylinder 5. A movable cylin drical collar 8 is arranged to be displaced to any desired position along the inner cylinder 6. The outer rim of the collar 8 extends into close proximity to the interior surface of cylinder 5 and capacitatively couples the inner cylinder 6 and the outer cylinder at the point where the collar is positioned at any time. Cylinder 5 may, as by grounding, be connected to the negative terminal 9 of a source of direct current, the positive terminal 10 of which is connected through a choke coil 1 l to the anode l2 of an ordinary hot cathode triode I3 suitable for generating high-frequency electrical oscillations. The triode l3 has a control electrode 14 and an electron-emissive cathode I5 which is supplied with current from an alternating-current source IS in the usual way. Each end of the cathode I5 is connected by a condenser I! to the cylinder 5, this being conveniently done by grounding the outer terminals of the condenser I! if the cylinder 5 is grounded.

The structure of the anode of the triode l3 will be more readily apparent from Figs. 3 and 4 which show the anode l2 as comprising a metallic thimble sealed to a glass tube mamber I8 having a reentrant press l9 through which are sealed the leads to cathode l5 and a lead 20 for the grid [4.

In order to effectively cool the anode 12, the latter is provided with a set of radiating metallic vanes 2| which may conveniently be welded to anode l2. The periphery of the vanes 2| is surrounded by a sheet-metal covering 22, and a sheet 23 of dielectric material of suitable thickness which may be mica is Wrapped around the metallic cylinder 22. Surrounding the mica layer 23 is a sheet-metal band 24, the ends of which are connected directly to the inner cyinder 6. In order to minimize the length of the high-frequency circuit, the end of the outer cylinder 5 may be very closely spaced from the band 24.

The grid l4 may be connected to the condensers I! by a resistor 25, and this may con veniently be done by grounding the end of the resistor 25 in cases where a plate of condenser I1 is grounded.

I have chosen to illustrate the tube l3 as being employed as an ultra-high-frequency amplifier, input current being fed to the grid I4 from an oscillator 26 of the required frequency, said oscillator 26 being provided with a resonant circuit comprising an inductor 21 and a capacitor 28 which are linked to the grid l4 through a coupling capacitor 29.

The foregoing relation of the circuit elements just described is schematically illustrated by Fig. 2 in which the reference numerals indicate the same structural elements as do the same numerals in Fig. 1. It will be seen that the elements 22, 23, 24 in Fig. l constitute the coupling capacitor marked 23 in Fig. 2.

By displacing the movable collar 8 lengthwise of cylinder 6, it will be found possible to tune the output circuit of triode l3 very effectively, and the energy in this output circuit may be drawn off for any desired purpose by means too well known in the art to require separate description.

To illustrate one specific embodiment of my invention which will work satisfactorily in practice, the cylinder 5 may be of sheet copper about 3 inches in diameter and about 12 inches long. The cylinder 6 may be of copper metal inch thick, 1% inches in external diameter and about 13 inches long. The movable collar 8 may be of copper metal 3% inches in external diameter and 1 inch long. The band 24 may be of sheet copper approximately 1 3' inch thick, 1% inches wide and having an internal diameter of approximately 2% inches. The dielectric 23 may be of mica approximately 0.002 inch thick and may extend at each end inch beyond the edge of the band 24. The cooling cylinder 22 may be of copper metal about 2 inches in internal diameter, t; inch thick and 2% inches long. The triode l3 may be of the type known as the WX3005 having an anode l2 about inch in outside diameter and 2 inches long. The tube portion l3 may be of glass about 2% inches in diameter and about 2 inches long. The grid 14 may be of tungsten wire about .020 inch in diameter having eight parallel conductors arranged in the form of a cage of .22" diameter. The cathode l5 may be of the thoriated type requiring 11.5 amperes at 4 volts to maintain it at a suitable operating temperature. The source of electromotive force 9, I0 may be of 1000 volts furnishing .25 ampere. The condensers I! may each be of about 0.001 microfarad capacity, and the shelves 2, 3 may be spaced about 8 inches apart. The resistor 25 may be of about 5000 ohms; the condenser 29 of about 0.0005 microfarad; the condenser 28 of about 0.00005 microfarad; and the inductor 21 of about .001 millihenry. The oscillator 26 may be of any desired type producing a frequency of about 100,000 kilocycles with power output of 30 Watts. example, it may comprise a tube of the 304-A type.

While I have described one particular embodiment of my invention in order to comply with the patent statutes, it will be recognized by those skilled in the art that its principles are of broader application in ways that will be evident to those versed in the radio art.

I claim as my invention:

1. In combination with an electrical discharge device having a cathode, a control electrode and an anode forming a portion of its wall, a layer of dielectric material upon said wall portion and a metallic covering in contact with the outer surface of said dielectric material to form a capacitor, a tuned output circuit coupled to said device by said capacitor, and means to supply alternating current between said control electrode and said cathode, said dielectric material constituting the main mechanical support for said discharge device.

2. In combination with an electrical discharge device having a cathode, a control electrode and an anode forming a portion of its Wall, a layer of dielectric material upon said Wall portion and a metallic covering in contact with the outer surface of said dielectric material to form a capacitor, a tuned output circuit comprising a pair of cylindrical surfaces and a movable member forming a capacitative coupling between them to constitute a variable reactance of the transmission line type, said output circuit being coupled to said device by said capacitor, and means to supply ultra-high-frequency alternating current between said control electrode and said cathode, said dielectric material constituting the main mechanical support for said discharge device.

For.

3. An electrical discharge device having a cathode, a control electrode and a cylindrical anode forming a wall portion thereof, a cylindrical conductor closely spaced away from said anode by insulating material to form a capacitor therewith, a tuned output circuit comprising a pair of cylindrical surfaces and a movable member forming a capacitative coupling between them to constitute a variable reactance of the transmission line type, said output circuit being coupled to said device by said capacitor, a structure supporting said output circuit, and means tosupply ultra-high-frequency alternating current between said control electrode and said cathode, said insulating material mechanically supporting said discharge device relative to said supporting structure.

4. An electrical discharge device having a cathode, a control electrode and a cylindrical anode forming a wall portion thereof, means extending radially outward from said anode to provide cooling-means therefor, a cylindrical conductor closely spaced away from said means by dielectric sheet material to form a capacitor therewith, a tuned output circuit comprising a pair of cylindrical surfaces and a movable member forming a capacitative coupling between them to constitute a variable reactance of the transmission line type, said output circuit being coupled to said device by said capacitor, and means to supply ultra-high-frequency alternating current between said control electrode and said cathode, said dielectric material constituting the main mechanical support for said discharge device.

SHELDON I. RAMBO. 

